submenu not working on mobile

Hi all, I have build the site in the free version of WP Hello Elementor and build it with the free elementor site builder. The site works fine but the mobile menu doesn’t work: the submenu only opens with small lines and only for a second. When I tab the lines the submenu shows for one second. If I’m fast enough I can open pages, but it disappears after a second.
Also the width of the mobile version is not good, but that’s probably another issue. (I’m not a pro in building sites..)
I tried adding the code in custom JS to keep it opened all times, but this also doesn’t work. (I read the code somewhere, I’m not that smart)

jQuery( document ).ready(function() {
  jQuery('.mobmenu-content .sub-menu').show();   
});

Can anyone help me with this?